87 lines
2.4 KiB
C++
87 lines
2.4 KiB
C++
/*
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* Copyright (c) 2014, 2015 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* random.cpp
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* Kernel entropy gathering.
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*/
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sortix/clock.h>
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#include <sortix/kernel/copy.h>
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#include <sortix/kernel/interlock.h>
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#include <sortix/kernel/syscall.h>
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#include <sortix/kernel/time.h>
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namespace Sortix {
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namespace Random {
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static unsigned long sequence = 0;
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bool HasEntropy()
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{
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// We only have new entropy once and that's at boot.
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return sequence == 0;
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}
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void GetEntropy(void* result, size_t size)
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{
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union
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{
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unsigned char buffer[256];
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struct
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{
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struct timespec realtime;
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struct timespec monotonic;
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unsigned long sequence;
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} seed;
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};
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if ( sizeof(buffer) < size )
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size = sizeof(buffer);
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// TODO: SECURITY: We need to actually gather entropy and deliver it.
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for ( size_t i = 0; i < size; i++ )
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buffer[i] = i;
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// NOTE: This is not random and is not meant to be random, this is just
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// meant to make the returned entropy a little different each time
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// until we have real randomness, even across reboots. The userland
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// arc4random mixer will mix it around and the produced streams will
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// look random and should not repeat in practice.
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seed.realtime = Time::Get(CLOCK_REALTIME);
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seed.monotonic = Time::Get(CLOCK_MONOTONIC);
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seed.sequence = InterlockedIncrement(&sequence).o;
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memcpy(result, buffer, size);
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}
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} // namespace Random
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} // namespace Sortix
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namespace Sortix {
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int sys_getentropy(void* user_buffer, size_t size)
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{
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unsigned char buffer[256];
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if ( sizeof(buffer) < size )
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return errno = EIO, -1;
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arc4random_buf(buffer, sizeof(buffer));
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if ( !CopyToUser(user_buffer, buffer, size) )
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return -1;
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return 0;
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}
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} // namespace Sortix
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